Polyurethane oil de-emulsifcation unit

ABSTRACT

A process for separating an aqueous emulsion including an aqueous phase and an non-aqueous phase into separated aqueous and non-aqueous phases, to provide a recovered non-aqueous phase, and to provide a recovered aqueous phase containing an acceptable level of the non-aqueous phase. In the process, at least one body, and preferably two or more bodies, of polymeric material, with a high surface area, typically a foam material or polymer chips, is used in a horizontal flow treatment system to break the emulsion and thus provide both the aqueous and non-aqueous phases as two separate flows. A wide range of polymers can be used in the system as the polymeric material including polyurethane, polypropylene, polystyrene, polyester, and polyethylene. If a very low level of non-aqueous phase in the effluent is required, for example to meet potable water standards, then a Kozlowski polyurethane, as described in U.S. Pat. No. 5,239,040 is preferred as the last polymeric material body.

The present application is a division of patent application Ser. No.10/363,028 filed on Aug. 5, 2003 which was the National stage ofInternational Application no. PCT/CA01/01284 filed on Sep. 7, 2001. Theentire content of said U.S. application Ser. No. 10/363,028 is hereinincorporated by reference.

In the recent past, there have been several well documented instances ofthe inadvertent spillage of liquids causing both environmental,ecological, and even toxicological problems for plant species, insects,wild life, and even people. Examples of spilled liquids include oils andsolvents, and a group of materials known loosely as PCB's. For many ofthese liquids, methods of clean up are known, even for relativelydifficult ones, such as crude oil and PCB's.

For many of these materials, a feasible method of both clean up andrecovery is described by Kozlowski, in U.S. Pat. No. 5,239,040. Thismethod has been shown to be both practical, and effective, in thatrather than simply dispersing the spilled liquid with, for example, adetergent, the spilled liquid itself is recovered. It is then possibleto separate the recovered liquid from the recovery agent so that therecovered liquid can be safely dealt with in an appropriate fashion, andso that the recovery agent itself an be re-used to capture more liquid.As described by Kozlowski, the recovery agent and the recovered liquidare separated by centrifugation. The recovery agent described Kozlowskiis a polyurethane foam material, which is prepared from specifiedreactants using a particular process. Hereafter this material will bedescribed as “Kozlowski polyurethane foam”.

In addition to its ability to function as a re-useable liquid recoveryagent, Kozlowski polyurethane has been shown to be useable to recover,for example, oil which has been spilled onto water. The Kozlowskipolyurethane has been shown to be able to absorb, for example, oil notonly when the foam is essentially dry but also when the foam isessentially fully wet or even waterlogged.

Another difficulty with spilt non-aqueous liquids arises when water ispresent. A water immiscible liquid can be present in association withwater in two quite different forms. At least a part of it will generallybe present as a discrete. second phase, which may be heavier or lighterthan water. The remainder will generally be present as an emulsion, ofat least some level of stability, and in which-water can be either thecontinuous phase or the disperse phase. In both cases, there is also thedifficulty that nearly all substances that appear to be immiscible withwater, for example light hydrocarbons such as benzene, in fact aresoluble in water to a small extent, often at a level of parts permillion. For an aqueous emulsion in which water is the continuous phase,Kozlowski, in WO 94/21347, disclosed that in addition to absorbing oildroplets dispersed as a second phase in water, Kozlowski polyurethane,even when water logged, will also absorb dissolved oil down to the lowlevels required for potable water.

In WO 94/21347 Kozlowski describes a water treatment procedure in whichthe tainted water is allowed to flow downwardly through successivelayers of Kozlowski polyurethane. The outflow of water has to bemonitored,, and the foam layers removed to recover absorbed oil fromthem when the oil level in the outflow-water rises to an unacceptablevalue.

Although the procedure described by Kozlowski in WO 94/21347 appears todeal with aqueous emulsions, in practise it has several disadvantages,the -most relevant one being that all of the oil, both as disperse phaseand as solute, has to be absorbed by the Kozlowski polyurethane,recovered from it typically by centrifugation, and the Kozlowskipolyurethane re-used to recover more oil. It is thus apparent thattreating a large volume of water containing only relatively smallamounts of emulsified oil can become very time consuming. There istherefore a need for an alternative technique to the use of Kozlowskipolyurethane, as described in WO 94/21347, at least as a primarytreatment for dealing with aqueous emulsions.

The only other apparently viable alternative for dealing with emulsionsis to flocculate the droplets until a size is reached at whichseparation into two phases will occur. This will generally requireflocculation to a droplet size in excess of at least 30 μm. However,this technique requires the consumption of chemicals and the creation ofa chemical sludge. It is consequently not environmentally friendly inuse.

This invention seeks to overcome these difficulties, and to provide atreatment apparatus and process which will deal with aqueous emulsionsreasonably quickly, and which will provide the non-aqueous phase in arecoverable form.

This invention is based on the discovery that not only Kozlowskipolyurethane foam, but also other polymeric materials when fabricatedinto a body of high surface area material such as a foam, if used underthe correct conditions, will function as an emulsion breaker, and willseparate a flow of an aqueous emulsion into two separate phases. It hasnow been found that when several polymeric materials when fabricatedinto a body of high surface area material are exposed, for example, to aflow of an emulsion of oil and water containing up to at least about10,000 ppm dispersed oil, two processes appear to take place. First, thepolymeric material absorbs oil until it becomes saturated with oil.Second, as the polymeric material continues to absorb more oil, itreleases as much oil as it absorbs, but it does so at a droplet sizewhich is sufficiently large to coalesce into a separate oil phase. It isthen possible to separate the aqueous and non-aqueous phases, andrecover each of the two phases separately. Further, by the use of asequence of treatment steps, the majority of the emulsified non-aqueousmaterial can be recovered, so that a Kozlowski polyurethane foamabsorbent only may be necessary for the last, or for the last few,treatment steps in the sequence. The only significant restrictions onthe polymer material appear to be first the ability to form a highsurface area material, such as a foam, from it, and second that thepolymeric material chosen is resistant to degradation under theconditions of use; for example, a polyester material is not suitableunder alkaline conditions which will result in hydrolytic degradation ofthe polymer, but which would be resisted by a polyalkylene such aspolyethylene.

Thus in its broadest embodiment, this invention seeks to provide aprocess for separating an aqueous emulsion having a continuous aqueousphase and an, non-aqueous disperse phase into separated aqueous andnon-aqueous phases, to provide a recovered non-aqueous phase, and toprovide a recovered aqueous phase containing an acceptable level of thenon-aqueous phase, which process comprises:

(a) contacting a flow of an aqueous emulsion with a first body ofpolymeric material having a high surface area;

(b) allowing the first body of polymeric material to become saturatedwith the non-aqueous phase of the emulsion;

(c) continuing the flow of aqueous emulsion until a separate non-aqueousphase is formed;

(d) separating the non-aqueous phase from the aqueous phase;

(e) recovering the separated non-aqueous phase;

(f) recovering a flow of treated aqueous phase; and

(g) if required, repeating steps (a) to (f) to contact the flow oftreated aqueous phase with at least a second body of polymeric materialhaving a high surface area until the acceptable level of non-aqueousmaterial is reached in the flow of recovered aqueous phase.

Preferably, the polymer used in the polymeric material is chosen fromthe group consisting of polyurethane, polypropylene, polystyrene,-polyester, and polyethylene. More preferably, the polymeric material ispolyurethane.

Preferably, the polymer material having a high surface area is apolymeric foam material. More preferably, the polymer material having ahigh surface area is a particulate polymeric foam material.Alternatively, the polymer material having a high surface area is in theform of polymer chips.

Preferably, the flow of aqueous emulsion in step (a) contacts the firstbody of polymeric material in a flow direction chosen from the groupconsisting of horizontal, vertical downwardly, and vertical upwardly.

Preferably, a plurality of bodies polymeric material is used, the flowcontacts each of them in sequence, and separated non-aqueous phase isrecovered from the flow after the each body of polymeric material.Alternatively, a plurality of bodies polymeric material is used, theflow contacts each of them in sequence, and separated non-aqueous phaseis recovered from the flow after the each body of polymeric materialexcept for the last, and separated non-aqueous phase is recovered fromthe last body.

Preferably, when a sequence of bodies of polymeric materials is used, atleast the last body of polymeric material comprises a Kozlowskipolyurethane foam.

Preferably, the process further includes pretreatment steps prior tostep (a) in which steps:

(h) non-aqueous phase droplets large enough to coalesce are allowed toform a separated non-aqueous phase,

(i) the separated non-aqueous phase is recovered, and

(j) the aqueous phase is recovered and used as the flow in step (a).

The invention will now be-described by way of reference to the attacheddrawings in which:

FIG. 1 shows schematically a three unit treatment system;

FIG. 2 shows schematically an alternative unit;

FIG. 3 shows graphically the performance of Kozlowski polyurethane andfour other commercially available polyurethane materials;

FIGS. 4, 5, 6 and 7 show graphically the performance of foams ofpolyurethane, polypropylene, polystyrene, polyester, and polyethylene.

Referring first to FIG. 1, this shows schematically a three compartmentunit together with a pretreatment unit. The treatment system 1 comprisesa set of boxes 2, 3, 4, 5, 6, 7 and 8. These can be fabricated asseparate units, or they can be fabricated in pairs as shown, or as asingle complete treatment system. A flow of incoming aqueous emulsion 9enters box 2, which is a pretreatment unit. The emulsion flow 9 willenter this box typically at about one third to one half way up from thebottom. In this box, any large droplets coalesce into a separatednon-aqueous phase 10, which is removed through the pipe 11.

The next box 3 has foraminous sidewalls 12 and 13, and a solid top sheet14. The box is packed with high surface area polymeric material 15,which is typically a foam. The foam is normally used in a particulateform, in part to assist in packing the box, and in part to ensure theexposure of a high surface area to the flow through the box. A typicalparticle size is from about 5 mm to about 20 mm. The separated aqueousemulsion phase 16 from box 2 enters box 3 through the wall 12, contactsthe polymeric material 15, and passes through wall 13 into box 4. In box3, further separation of the non-aqueous and aqueous phases occurs. Inbox 4, the two phases separate to provide a second separated non-aqueousphase 17 which is recovered through the pipe 18, and a treated aqueousphase 19 passes to box 5. As shown, box 4 includes an enlarged optionalcatchment space extending over the top of box 3.

Boxes 5 and 6 are constructed in the same way as boxes 3 and 4. Treatedaqueous phase 19 enters box 5 through the foraminous wall 20, contactsthe polymeric material 21, and leaves through foraminous wall 22. In box6 further non-aqueous phase 23 separates, is collected, and recoveredthrough the pipe 24. Twice treated aqueous phase 25 passes to boxes 7and 8, which again are the same as boxes 3 and 4, with a third body ofpolymeric material between two foraminous walls. In box 8 furthernon-aqueous phase 26 is collected and recovered through pipe 27, and aflow 28 of treated aqueous phase leaves the system from box 8. In eachof pipes 18, 24 and 27 a suitable flow control device is used, such as afloat operated automatic valve, or a time sequenced valve.

In the treatment system, the flow rate of incoming aqueous emulsion 9 isadjusted so that there is an adequate contact time between the aqueousemulsion and the polymeric material in boxes 3, 5 and 7 to effectseparation of the non-aqueous phase, and to form a free floatingnon-aqueous phase layer. In practise, this is generally found to besufficient to provide droplets having a size in excess of at least about150 μm.

If the acceptable level of non-aqueous phase in the treated aqueousphase 28 is extremely low, for example if the treated aqueous phase isintended to meet the standards for potable water, then it is recommendedthat at least the third body of polymeric material in box 7 should beKozlowski polyurethane foam. In that case, the Kozlowski polyurethanefoam will be acting as an absorbent only, and not as an emulsionbreaker. Consequently, when the third body—or the last if more thanthree are used—is a Kozlowski polyurethane foam functioning as only anabsorbent, a separate non-aqueous phase will not be formed, and therewill not be a non-aqueous phase flow in pipe 27. Instead, the treatedaqueous phase has to be monitored, so that when the Kozlowskipolyurethane foam becomes fully loaded with non-aqueous phase (whichwill be indicated by a rise in concentration in the treated flow 28) itis removed, and the non-aqueous phase recovered from it, typically bycentrifugation. In order to avoid having to cease processing whilenon-aqueous phase is recovered from the loaded Kozlowski polyurethane,it is convenient to provide two treatment units in parallel, which areused alternately.

Similarly, if the incoming aqueous flow 9 is heavily contaminated withthe non-aqueous phase, more than three polymeric material bodies may berequired. The number required will be largely determined by the level ofcontamination which is acceptable in the effluent water from thetreatment unit. If the incoming aqueous flow also-contains solidmaterial, it is advantageous to provide a vent 29 from box 2 so thataccumulated solids can be periodically removed.

The polymeric material in the first compartment may also need to beinspected periodically, and replaced if it becomes clogged withsuspended small particle size solids in the aqueous flow which have notbeen separated in a pretreatment stage.

This unit has the advantage that the non-aqueous phase droplets as theyare detached from the body of polymeric-material simply continue to riseaway from it, and it is only the treated flow which moves laterally.

In FIG. 1 the flow of aqueous emulsion through the bodied ofpolyurethane material in treatment stages is essentially horizontal. Itis also possible to arrange the treatment stages so that the flow passesthrough the polyurethane body essentially vertically, in either anupward or a downward direction. A suitable treatment unit is shown inFIG. 2 in which the flow passes in an upward direction.

In FIG. 2 the treatment unit 40 as shown is essentially a singlestructure: like the horizontal unit it can be made as one integralstructure or from several separate interconnected boxes. Aqueousemulsion enters the bottom of the unit through a pipe as at 41 into thefirst box 43. If desired, a drain 42 can be provided to deal with anysolids that accumulate in box 43. The boxes then alternate upwardly:boxes 43, 45, 47 and 49 contain the aqueous phase flowing through thetreatment unit, and boxes 44, 46 and 48 contain the high surface areapolymeric material. Catchment boxes 50, 51, 52 and 53 are then locatedbeside each pair of boxes. The construction and operation of boxes 43,44 and 50 is exemplary. The polymeric material is located on a grid 54,such as a perforated metal. plate, and between the outer solid wall 56Aand inner wall 56B. The wall 56B includes a row of perforations or slotsacross the box 43 just below the grid 54. The top surface 57 of thecatchment box 57 is solid. As the emulsion encounters the saturated bodyof polymeric material body 58, the aqueous phase continues more or lessupwardly through it, and into the next box. If desired, a secondperforated metal plate 55 can be located above the body of polymericmaterial 58. As the polymeric material breaks the emulsion, theseparated oil droplets tend to collect on its lower surface, and tendnot to percolate through it; the separated oil droplets travel sidewaysthrough the perforations or slots in wall 56B into the catchment box 50.Separated oil collects as a second phase as at 59, and is removedthrough the pipe 60. Flow through the pipe 60 is again controlled in anysuitable way, for example a float controlled automatic valve or a timesequenced valve. The two following units operate in the same way, toprovide a treated water flow into the following box above, and an oilflow in the pipes 61 and 62.

How the last box 49, together-with its catchment box 53, operate dependson the amount of oil still in the aqueous emulsion flow reaching it, andthe amount of oil that can be accepted in the effluent treated waterflow 64. In order to separate any free oil in the incoming water asuitable wire arrangement is provided between the box 49 and thecatchment box 53. If the last body of polymeric material in box 48 isKozlowski polyurethane foam that is functioning only as an absorbent,then there should be no separated oil flow into the catchment box 53,and hence no oil flow in the pipe 63. In the alternative, if the lastbody of polymeric material in box 48 is functioning to separate furtheroil, then it is possible that there can be some oil droplets in thewater in box 49. These are then trapped in the catchment box 53, andrecovered as an oil phase through pipe 63.

As described, the treatment unit in FIG. 2 includes three polyurethanebodies. How many bodies are used will be determined by essentially threefactors: the quantity of emulsion to be treated, the amount ofnon-aqueous material in the emulsion, and the quality level required inthe outflow of treated water. It is therefore possible the more than thethree units shown will be required in some cases. Since units of thistype are often required to be used either under adverse conditions, orunder conditions where only minimal supervision is possible, it ispreferred that the number of treatment-units used should be more thananalyses indicate to be required, thus providing a safety margin.

In the practise of this invention, as noted above, if a very low levelof non-aqueous material in the aqueous phase is required it is usuallydesirable to use a Kozlowski polyurethane in at least the last treatmentstage. For the earlier stage, or stages, other polymeric materials canbe used. FIG. 3 shows comparative performance data for five differentpolyurethane materials. This data is based on a single pass test, inwhich an aqueous oil emulsion was passed through a body of each foammaterial, and the oil content at both inlet and outlet was determined.In these tests, a 10 cm diameter pipe was used containing fivecompartments. The first and third compartments, each about 4 cm inlength, contained the test sample of polyurethane. The first, third andfifth compartment were empty, and about 0.8 cm in length. The flowthrough the test pipe was horizontal. The emulsion used was 10W30 motoroil mixed into water using a centrifugal pump at 3,450 rpm. The flowrate was constant, at 1.5 L/min.

In FIG. 3, the effluent oil level(vertical axis) is plotted against theinlet oil level(horizontal axis), in ppm on both axes.

The five polyurethane materials are identified as follows.

A: Kozlowski polyurethane foam.

B: Upholstery grade foam chips, composition unknown.

C: Great Stuff™ polyurethane foam.

D: Great-Stuff™ expanding polyurethane foam.

E: All Direction Great Stuff™ polyurethane foam.

Product B is a standard commercial product available from many sources;its composition is not known. The product was supplied by Eversoft Fibreand Foam Ltd. Products C, D and E are all commercially available, andare made by Flexible Products Co., Joliet, Ill., USA. The maincomponents appear to be 4,4′1-diphenylmethanediisocyante, apolyether/polyol blend, and a blowing agent. As FIG. 3 shows, all ofthese products are capable of significantly reducing the oil content ofthe oil and water system tested.

FIGS. 4, 5, 6 and 7 the results of similar test are shown using otherpolymeric materials, with a polyurethane foam included for comparison.In these tests, the cylinder. contained four compartments packed withthe polymeric material, the flow rate was 1.2 litres/minute, and thetest oil in the emulsion was 10W30 motor oil. The test polymers usedwere:

in FIG. 4, polyethylene;

in FIG. 5, polyester;

in FIG. 6, polystyrene; and

in FIG. 7, polypropylene.

The polyester and polyurethane were used as foams; the polyethylene,polystyrene and polypropylene were used as high surface area smallparticles, which were thin cutting chips(similar to swarf) with amaximum dimension of about 5 mm. In each experiment, the mixture of oiland water was passed through the cylinder, and the oil level measuredbefore and after treatment. The oil level in the aqueous flow was notconstant.

In each of FIGS. 4-7 the horizontal axis is time in hours; and thevertical axes are in parts per million (ppm). The left axis refers tothe treated aqueous flow, and the right axis to the untreated aqueousflow; these axes are not to the same scale. In each Figure, trace A isthe incoming aqueous oil containing flow; trace B is after treatmentwith polyurethane, and trace C is after treatment with the test polymer.In each Figure the traces show that the amount of oil left in theaqueous flow is related to the amount of oil present initially. Thesetraces also show that of the materials tested, the polyurethane appearsto be the most effective, and reduces the oil level to generally lessthan a maximum of about 50 ppm.

1. A process for separating an aqueous emulsion including an aqueouscontinuous phase and an non-aqueous disperse phase into separatedaqueous and non-aqueous phases, to provide a recovered non-aqueousphase, and to provide a recovered aqueous phase containing an acceptablelevel of the non-aqueous phase, which process comprises: (a) contactinga flow of an aqueous emulsion with a first body of polymeric materialhaving a high surface area; (b) allowing the first body of polymericmaterial to become saturated with the non-aqueous phase of the emulsion;(c) continuing the flow of aqueous emulsion until a separate non-aqueousphase is formed; (d) separating the non-aqueous phase from the aqueousphase; (e) recovering the separated non-aqueous phase; (f) recovering aflow of treated aqueous phase; and (g) if required, repeating steps (a)to (f) to contact the flow of treated aqueous phase with at least asecond body of polymeric material having a high surface area until theacceptable level of non-aqueous material is reached in-the flow ofrecovered aqueous phase.
 2. A process according to claim 1 wherein thepolymer in the polymeric material is chosen from the group consisting ofpolyurethane, polypropylene, polystyrene, polyester, and polyethylene.3. A process according to claim 2 wherein the polymer in the polymericmaterial is polyurethane.
 4. A process according to claim 1 wherein thepolymer material having a high surface area is in a form chosen from thegroup consisting of foam and high surface area chips.
 5. A processaccording to claim 4 wherein the polymer material having a high surfacearea is a particulate polymeric foam material.
 6. A process according toclaim 1 wherein a plurality of bodies polymeric material is used, theflow contacts each of them in sequence, and separated non-aqueous phaseis recovered from the flow after the each body of polymeric material. 7.A process according to claim 1 wherein a plurality of bodies polymericmaterial is used, the flow contacts each of them in sequence, andseparated non-aqueous phase is recovered from the flow after the eachbody of polymeric material except for the last, and separatednon-aqueous phase is recovered from the last body.
 8. A processaccording to claim 1 wherein, when a sequence of bodies of polymericmaterials is used, at least the last body of polyurethane materialcomprises a Kozlowski polyurethane.
 9. A process according to claim 1which further includes pretreatment steps prior to step (a) in whichsteps: (h) non-aqueous phase droplets large enough to coalesce areallowed to form a separated non-aqueous phase, (i) the separatednon-aqueous phase is recovered, and (j) the aqueous phase-is recoveredand used as the flow in step (a).